1. Field of the Invention
The present invention relates to an easily tearable laminated film and a method of manufacturing the same and, more particularly, to an easily tearable laminated film capable of being easily torn in a specific intended direction and suitable as a packaging material.
2. Description of Related Art
Various types of liquid and powder products such as liquid soup, powder soup, and powder medicines are individually packaged by a composite or laminated packaging material formed using an organic resin film as a base, and are used in this sealed state. In opening these sealed bags, the bags are required to be easily torn so that the contents neither spill nor scatter.
For this reason, the following sealed bags given easy tearability have been conventionally developed.
(1) In manufacturing a sealed bag from a laminated film, a sealed portion is so formed as to position in a film portion inside the peripheral edge of the film. An unbonded film edge portion is left outside the sealed portion, and a V-shaped notch is formed in this film edge portion. This sealed bag can be torn starting from the V-shaped notch.
(2) In manufacturing a sealed bag from a three-layer film, a sealed portion is so formed as to position in a film portion inside the peripheral edge of the film. An unbonded film edge portion is left outside the sealed portion, and a V-shaped notch is formed in this film edge portion. Additionally, a large number of slits are formed along the extension line of the V-shaped notch in a film on the outside (Jpn. UM application. KOKAI Publication No. 61-66137). This sealed bag can be torn in the formation direction of the slits starting from the V-shaped notch.
(3) In manufacturing a sealed bag from a laminated film, sealed portions are so formed as to position in film portions inside two peripheral edges perpendicular to an opening portion. An unbonded film edge portion is formed outside these sealed portions, and a scar portion having a large number of band-like scars is formed in each film edge portion (Jpn. UM application. KOKAI Publication No. 5-178352). An easily openable sealed bag of this type can be torn from an arbitrary position of the film edge portions.
The sealed bags (1) to (3) described above are manufactured by using, as a base film, a polyethylene film or an unstretched polypropylene film having good heat-sealing properties with which the film can be readily formed into a bag. Unfortunately, these base films are difficult to tear in either the longitudinal or lateral direction. For this reason, the sealed bag (1) having a V-shaped notch is in many cases inconvenient in that the bag is torn from the V-shaped notch in the oblique direction, rather than in the lateral direction as the direction of the extension line of the notch, and consequently the contents scatter out of the bag.
The sealed bag (2) in which a V-shaped notch and slits are formed is improved in the easy tearability as compared with the sealed bag (1). However, the cost of the sealed bag is increased since a cumbersome operation for forming a large number of slits in the outer layer of the multilayer film is necessary.
The sealed bag (3) in which a scar portion having a large number of band-like scars is formed in the peripheral edge of an unbonded film is readily tearable from any arbitrary portion. As with the V-shaped notch, however, the scar portion merely functions as the starting point of tear. Consequently, the bag is torn obliquely and the contents scatter in many cases.
Among other known sealed bags given linear easy tearability are those for gum and cigarettes, in which a tape is bonded in the tearing direction and one end of the tape is left unbonded and protrudes. This sealed bag can be linearly torn by holding the protruding end of the tape and pulling the end along the tape. It is unfortunate that not only the tape is additionally required in the manufacturing process of the sealed bag, but also the step of bonding the tape to the film is added to the process. This increases the manufacturing cost of the sealed bag.